Amazon’s AWS customers have noticed that since the Meltdown patch was rolled out in December there has been an increase in CPU utilisation by their EC2 virtual machines. Customers are unhappy because it’s forcing them to choose between optimising their application code or to move to more powerful hardware to compensate for the slowdown.

Responding to criticisms from customers, an Amazon employee said:

“The update that is being applied to a portion of EC2 instances can, in some corner cases, require additional CPU resources … For some time we have recommended that customers use our latest generation instances with HVM AMIs to get the best performance from EC2. If moving to a HVM based AMI is not easy, changing your instance size to m3.medium, which provides more compute that m1.medium at a lower price may be a workaround.”

According to a statement issued by Amazon, the patch shouldn’t impact most customers' workloads but for those which are impacted, the company has said it will work with those customers to help resolve problems. The patch’s impact is likely not limited to AWS so you may also notice a slowdown on other clouds such as Microsoft’s Azure and Google’s Compute Engine too.